This invention relates to a superconducting device which comprises a Josephson junction element and at least one third electrode for injection of quasiparticles attached to the Josephson junction element and serves for the purpose of controlling the current-voltage characteristic of the Josephson junction, the superconducting critical current, and the Josephson junction voltage.
The tremendous advance achieved in electronic technology in recent years has made various industrial branches specializing in data processing, space telecommunication, instrumentation, etc. feel a strong need for early realization of ultrahigh-speed switching of signals, high-sensitivity low-noise detection and amplification of high-frequency signals, and the like.
The growth of electronic technology has to date been promoted by the development of devices comprised mainly of semiconductors, particularly transistors. With a view to permitting further increase of the speed of signal transmission and satisfying the demand for energy saving, extensive research is now under way toward the development of devices which are formed mainly of superconductors and adapted to operate under extremely low (cryogenic) temperatures.
In the conventional cryogenic devices of this nature, the commonest method adopted for controlling the characteristics of the Josephson junction element comprises disposing control lines close to the element and effecting the required control using the magnetic fields generated by the control lines. By this method, however, the number of layers required for the lines inevitably increases, raising the chance of the devices suffering from line breakage, short-circuiting and other failures and from degradation of reliability of performance. Thus, it has not been easy for the devices to be integrated as desired.